Help : Merging Binary Search Trees

[ptrSriram]

Can someone help me with an algorithm to merge two binary search trees.

One method I thought of was to flatten both the trees into sorted
lists(inorder traversal),merge those two sorted lists, and build a
binary search tree from the new list.
But this seems to be expensive in terms of space. Can this be done more
efficiently ?
Please help me.

 

[Walter Roberson]

Can someone help me with an algorithm to merge two binary search trees.

One method I thought of was to flatten both the trees into sorted
lists(inorder traversal),merge those two sorted lists, and build a
binary search tree from the new list.
But this seems to be expensive in terms of space. Can this be done more
efficiently ?

That depends. There are a number of different types of binary trees.
Is there some particular property imposed on the trees you are
using, such as that they must be "balanced" ? Do your tree entries
have back-pointers or just downward pointers?

 

[Chuck F.]

That depends. There are a number of different types of binary
trees. Is there some particular property imposed on the trees
you are using, such as that they must be "balanced" ? Do your
tree entries have back-pointers or just downward pointers?

I think the question should be answered in terms of a minimal
organization. i.e. the fundamental data item should be very
similar to:

struct itemlink {
struct itemlink *left, *right;
void *dataptr;
};

together with some routine that will return a -1, 0, +1 comparison
result when passed two struct itemlink * pointers. Then the trees
to be merged are represented by two struct itemlink * pointers to
the roots of the two trees.

 

[Thad Smith]

Can someone help me with an algorithm to merge two binary search trees.

One method I thought of was to flatten both the trees into sorted
lists(inorder traversal),merge those two sorted lists, and build a
binary search tree from the new list.
But this seems to be expensive in terms of space.

Why would it be expensive in space? If the data is in a tree, each item
should be held in a node with two or more pointers. You should be able
to link the items into list, merge them, and place them in another tree
without any additional space.